Invisible information detecting apparatus

ABSTRACT

An invisible information detection apparatus includes parts that irradiate a light onto a medium, detect infrared light generated from the medium, and judge a specific pattern consisting of a combination of two areas on the medium in accordance with the detection result. One of the areas represents higher reflectance than the reflectance of the medium in substantially the same infrared wavelength region, and the other area represents lower reflectance than that of the medium. An invisible information detection method comprises an irradiation step, a detection step and a judgment step. The judgment step judges a specific pattern of a combination of two areas on the medium in accordance with the result from the detection step. One of the areas represents higher reflectance, and the other area represents lower reflectance, as compared to the reflectance of the medium, in substantially the same infrared wavelength region.

This application is a division of application Ser. No. 08/184,502 filedJan. 19, 1994, now U.S. Pat. No. 5,503,904.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an invisible information recordedmedium on which invisible information has been recorded, a detectingapparatus for detecting the invisible information and a recording agentfor recording the invisible information.

2. Related Background Art

(1) Hitherto, the trend of improving the performance of copying machinesarises a risk of forgery of bills, securities and notes and the like.Therefore, there arises a necessity of judging whether or not forgery ofthe bill or the like has been performed. Further, the forgery of thebills must be previously detected and prevented. In order to prevent theforgery, there have suggested a marking method using a ultraviolet rayexciting fluorescent pigment, a method using a diffraction phenomenonsuch as hologram, a method of applying a magnetic substance to bedetected by a magnetic head, a method using color change occurring dueto photochromism and a method of discriminating a specific image, suchas a bill, by image recognition.

(2) With the improvement in the performance of the copying machine andso forth, copying of various information items can easily be performed.

On the other hand, privacy guarding and trade secret confidence havebeen considered important, causing a problem to arise in that copyingcan easily be performed.

Hitherto, the foregoing copying has been prevented by bonding a specialfilm to the document or the like to cause the copied image to bedeteriorated or to cause the forgery to be informed.

(3) A method has been known which is arranged in such a manner that animage is formed on the surface of a photoconductive material by anelectrostatic method and then the image is developed. As disclosed inU.S. Pat. No. 2,297,691 filed by C. F. Carlson, the basicelectrophotographic method comprises the steps of uniformly loadingstatic electricity onto a photoconductive insulating layer, exposing thelayer to a light and dark image to delete the electric charge of theregion exposed to light, and allowing fine substance called a toner toadhere to an electrostatic latent image thus-obtained so that theforegoing electrostatic latent image is developed.

The toner is usually attracted to a region of a layer in which thecharge is left, causing a toner image corresponding to the electrostaticlatent image to be formed.

Then, the thus-formed powder image can be transferred onto the surfaceof a supporting member, such as paper. The transferred image canpermanently be secured onto the surface of the supporting member with,for example, heat.

In place of forming the latent image by uniformly charging the layer ofthe photoconductive layer and by exposing the layer to the light anddark image, the latent image may be formed by directly charging thelayer in the form of the image.

If the process of transferring the powder image is intended to beomitted, the powder image may be secured to the photoconductive layer.Another method may be employed in which an adequate fixing means, suchas solvent treatment or outer layer coating process, is employed inplace of the heat fixing process.

There have been some known methods of using toner particles as theelectrostatic latent image to be developed. One of the developingmethods has been disclosed in U.S. Pat. No. 2,618,552 filed by E. N.Wise which is a cascade development method.

The cascade development method comprises the steps of carrying adeveloper composed of relatively large carrier particles having finetone particles electrostatically coated on the carrier to the surface ofelectrostatic latent image carrying surface as to be rolled or cascaded.

The composition of the carrier particles is so selected that the tonerparticles are charged in a frictional charge manner to a desiredpolarity.

When the mixture is cascaded or rolled while exceeding the developmentcarrying surface, the toner particles are allowed to electrostaticallyadhere and secure to the charged portion of the dissolved image but thesame does not adhere to the portion, in which the image is not charged,that is, the base portion.

The toner particles accidentally allowed to adhere to the base portionare substantially removed with the rolling carrier due to a fact thatthe electrostatic attractive force between the toner and the carrier islarger than that between the toner and the non-charged base portion.

The carrier and the excess toner are then recirculated. The foregoingmethod is significantly effective to develop a linear copied image.

Another method for developing the electrostatic image is a magneticbrush method as disclosed in, for example, U.S. Pat. No. 2,874,063. Theforegoing method comprises the step of carrying a developing substancecontaining a toner and magnetic carrier particles with a magnet. Themagnetic field of the magnet arranges the magnetic carrier to be formedinto a brush-like shape. The magnetic brush comes in contact with thesurface of the electrostatic image carrying surface, causing the tonerparticles to be attracted from the brush to the latent image with theelectrostatic attractive force.

Another method capable of developing the electrostatic latent image is apowder cloud method as disclosed in, for example, U.S. Pat. No.2,221,776 filed by C. F. Carlson. The foregoing method comprises thestep of allowing to pass a developing substance containing electricallycharged toner particles in a gaseous fluid through a position adjacentto the surface carrying the electrostatic latent image. The tonerparticles are attracted from the gas to the latent image by theelectrostatic attractive force. The foregoing method is significantlyeffective to develop an image in which light portions and dark portionsare distributed continuously.

A touch-down method disclosed in U.S. Pat. No. 3,166,432 filed by R. W.Gundlach may be employed if necessary.

Among the foregoing available methods, the magnetic brush method hasbeen widely used.

Although the foregoing methods are used to make a black and white copiedproduct, they are able to form an image in another color or an imageformed by combining colors.

Similarly to another coloring method, an electrophotographic coloringmethod is usually based on a color-additive or subtractive colorformation type synthesis of three colors. That is, if theelectrophotographic method is performed in a full color manner, three ormore color toners, that is, developing particles must be used tosynthesize any desired color.

In order to color-copy a full-color original, three or more colordecomposed images are mutually matched and combined with one another. Inthe color electrophotography, three or more electrostatic images are, asdescribed above, generated by exposing a photosensitive member to anoptical color decomposed image as disclosed in, for example, U.S. Pat.No. 2,962,374.

The electrostatic latent images respectively are developed by differentcolor toners, and then the three-type toner images are combined witheach other so that a final image is formed. The combination of the threecolor toner images are usually formed on a copying sheet, such as paper,and the toner image is permanently fixed on the sheet.

The most ordinary method for fixing the toner images on a paper copyingsheet is a method comprising the steps of using a resin toner containinga coloring agent and fusing the toner image onto the copying sheet withheat.

The image may be fixed by another method, for example, it is exposed tomolten vapor. With the progress of the copying method, informationconfidence becomes an important fact.

Forgery copying has been prevented by a method comprising the step ofbonding a special film to the document or the like to deteriorate thequality of the copied image or a method of clearing the forgery copying.

(1) However, the method using the ultraviolet rays exciting fluorescentpigment encounters a problem in that a countermeasure can be takenbecause the fluorescent pigment can easily be detected by an ultravioletirradiation means, such as a black lamp. Further, the necessity of usinga ultraviolet ray source in the apparatus makes the optical system to becomplicated. The method using the diffraction phenomenon, such ashologram, encounters a problem in that the formation of the mark on thebill or the like raises the cost. The method of applying the magneticsubstance arises a necessity of bringing the bill or the like intocontact with the magnetic head in a hermetical manner, causing a problemto arise in that the structure to be complicated. The method usingphotochromism suffers from instability of the photochromism compound.The method based on the image recognition requires a large quantity ofdata to recognize all bills and securities and so forth, causing a heavyload to be burden by the apparatus and the cost to be enlarged.

Another method using near infrared fluorescent has been disclosed toovercome the foregoing problems, so that a long life light emittingdiode is enabled to be used, and therefore an influence of contaminationcan be prevented satisfactorily.

If the near infrared ray absorbing film or the like is used between thedetecting apparatus and the original document, there arises a problem inthat the detection cannot easily be performed. The necessity ofindividually using a light emitting diode and a photodiode sensitive tolong wavelength causes the structure of the apparatus to be complicated.

(2) However, each of the foregoing conventional methods has beenstructured to correspond to analog copying machines. Therefore, it hasbeen difficult to prevent the forgery copying and reading in a copyingmachine or a printer comprising a reading unit using a CCD or the like.

Therefore, it is preferable that the detection apparatus identifies thatthe recorded medium is the copy and read inhibited medium to stop theoperation.

Each of the foregoing identifying marks has a problem.

(3) However, each of the foregoing conventional methods has beenstructured to correspond to analog copying machines. Therefore, it isunsatisfactory to realize secret confidence with a copying machine or aprinter comprising a reading unit using a CCD or the like. The fact thatthe easy recognition arises a problem in that an effective secretconfidence method has not been realized against reproduction writing andphotography.

SUMMARY OF THE INVENTION

The present invention is directed to overcome the foregoing problems.Accordingly, an object of the present invention is to provide a recordedmedium on which invisible information is recorded to cheaply andassuredly judging a specific image, such as a bill, and an invisibleinformation detecting apparatus for detecting and using the mark.

Another object of the present invention is to provide an invisibleinformation recorded medium serving as recording paper with which a factthat the subject original document is a copy inhibited special originaldocument can easily be identified.

Another object of the present invention is to provide a novel recordingagent for use in an image forming apparatus, such as a copying machine,and more particularly in an electrophotographic apparatus.

In order to achieve the foregoing objects, according to one aspect ofthe present invention, there is provided an invisible informationrecorded medium comprising an identification mark recorded tehreon, saididentification mark being composed of a region having a high reflectanceand a region having a low reflectance in the same near infraredwavelength as compared with the reflectance of said medium.

According to another aspect of the present invention, there is providedan invisible information detecting apparatus comprising: detection meansfor detecting a region having a high reflectance and a region having alow reflectance with respect to the reflectance of the medium in thesame infrared ray region; and judging means for judging a specificoriginal document in accordance with the results of detection performedby said detection means.

According to another aspect of the present invention, there is providedan invisible information recorded medium for use to record image,comprising: a visible region having no information recorded thereon; andan identification mark, the reflectance of which is changed in the nearinfrared ray region.

According to another aspect of the present invention, there is provideda recording agent comprising toner particles containing a resin and acoloring material, wherein said coloring material is near infrared rayabsorbing coloring material or pigment free from absorption in a visibleregion and absorbed in the near infrared ray region.

Other and further objects, features and advantages of the invention willbe appear more fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are structural views which illustrate a specificoriginal document identification pattern according to a first embodimentof the present invention;

FIG. 2 is a structural view which illustrates a color copying apparatusemploying the structure according to the present invention;

FIG. 3 is a structural view which illustrates a specific originaldocument identification pattern according to a fourth embodiment of thepresent invention;

FIG. 4 is a 2D-area signal generating portion for detecting the specificpattern according to the first embodiment of the present invention;

FIG. 5 illustrates a reference pixel for detecting the specific patternaccording to the first embodiment of the present invention;

FIG. 6 is a structural view which illustrates a specific patternjudgment portion according to the first embodiment of the presentinvention;

FIGS. 7A and 7B are structural views which illustrate a CCD according tothe first embodiment of the present invention;

FIG. 8 illustrates a spectrum reflectance of a standard white plate;

FIG. 9 illustrates a spectrum transmission ratio of a specific pattern;

FIG. 10 are graphs which illustrate spectral sensitivity characteristicsof a visible line sensor and characteristics of a filter for an infraredray reading sensor according to this embodiment;

FIG. 11 illustrates characteristics of a dichroic filter for cuttinginfrared rays;

FIG. 12 illustrates characteristics of a filter for cutting far infraredrays;

FIG. 13 is a view which illustrates a state where an infrared raycutting glass is fastened to a CCD sensor;

FIG. 14 is a view which illustrates a fastened cover glass in a casewhere the glass for cutting infrared rays is disposed on the cover glassof the CCD;

FIG. 15 is comprised of FIGS. 15A and 15B illustrate an image signalcontrol portion;

FIG. 16 is a timing chart of an image control signal;

FIG. 17 is a flow chart for control performed by a CPU;

FIGS. 18A and 18B are structural views which illustrate an image readingapparatus according to a second embodiment of the present invention;

FIGS. 19A and 19B are structural views which illustrate an image readingapparatus according to a third embodiment of the present invention;

FIGS. 20A and 20B illustrate absorption spectrum and fluorescentspectrum of an ink (fluorescent coloring material) for use in a highreflectance portion of the specific pattern;

FIG. 21 illustrates reflection spectrum of a medium having theidentification pattern recorded thereon;

FIG. 22 illustrates reflection spectrum of an image recorded with thetoner according to the present invention; and

FIG. 23 illustrates a transmission spectrum of a filter for the CCD foruse to reproduce information recorded with the toner according to thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

First Embodiment

This embodiment is arranged in such a manner that a invisibleinformation recorded medium having an identification mark, which iscomposed of a region having a relatively high reflectance as comparedwith the reflectance of a medium at the same near infrared wavelengthand a region having a low reflectance, and an apparatus for detectingthe medium are used to assuredly judge a specific original document witha low cost.

Further, the specific original document can be judged while preventingan erroneous recognition in a case where a judgment prevention isperformed while using an infrared ray absorption film or an infraredreflective film.

Preferred embodiments of the present invention will now be described.

The operation of recording the region will now be described which has ahigher reflectance as compared with the reflectance of a medium andarranged to be used to record an identification mark having invisibleinformation recorded for recognizing bills, securities and notes and thelike (copy inhibited original documents which are subjects of theforgery inhibition) and inhibiting copying of them. Fluorescent coloringmaterial or pigment is dissolved or dispersed in a binder so that apredetermined pattern is formed on the copy inhibition original documentby printing or the like. The fluorescent coloring material or pigmentmay be a material having the fluorescent wavelength peak in a range of700 nm or longer, preferably 750 nm or longer. Since the material havingthe fluorescent wavelength peak in a range of 700 nm or shorter can bevisually detected, the secrecy cannot satisfactorily be maintained. If amaterial having the fluorescent wavelength peak in a range of 1100 nm orlonger is used, sensitivity of a Si-type photo-detection device, such asa CCD, deteriorates. In this case, the identification mark cannotaccurately be judged. It is further preferable to employ a fluorescentcoloring material or pigment having the fluorescent wavelength peak in arange of 1000 nm or shorter. Since the near infrared fluorescent rayscan be detected when they are separated from exciting rays, it ispreferable that the two types of the rays have wavelengths which areconsiderably different from each other. Therefore, near infraredfluorescent coloring material or pigment and exciting rays are selectedsuch that they are different from each other by 50 nm or more,preferably 100 nm or more. The exciting wavelength is selected dependingupon the type of the light source and the spectral filter.

The near infrared fluorescent coloring material may be a xanthene,oxazine, thiazine, polymethine or stryl compound. As an inorganiccompound, a solid laser material of a type containing a rare earthelement is used.

More specifically, any one of the following near infrared fluorescentcoloring material may be used. However, a material may be usedregardless of the exemplified materials if it has fluorescent rays inthe near infrared ray region and exhibits excellent fluorescent quantumyield, weather and light resistance.

Compounds (1) to (61)

The binder resin for use in the foregoing near infrared fluorescentcoloring material or pigment may be a urea resin, melamine resin, alkydresin, acryl resin, vinyl chloride resin, aromatic sulfonamide resin, ora benzoquanamine resin or their copolymer. By using a ultravioletabsorber or an anti-oxidant with the foregoing resin, the lightresistance of the resin can be improved. The binder resin can bemanufactured by a block resin crushing method, emulsificationpolymerizing method or a resin precipitation method or the like.

    __________________________________________________________________________    (1)                                                                               ##STR1##                                         X =  CN abs 680 nm       (2)                                                                               ##STR2##                                         X =  CN abs 650 nm       (3)                                                                               ##STR3##                                         X =  CN abs 710 nm       (4)                                                                               ##STR4##                                         X =  I Y =  Cl Rose                                                           Bengale                  (5)                                                                               ##STR5##                                         Naphthalo-                                                                    fluorescein 126          (6)                                                                               ##STR6##                                         Carbazine 122            (7)                                                                               ##STR7##                                         Victoria Blue R          (8)                                                                               ##STR8##                                         abs 650 nm               (9)                                                                               ##STR9##                                         abs 620 nm               (10)                                                                              ##STR10##                                        n =  3 abs 690 nm        (11)                                                                              ##STR11##                                        abs 680 nm               (12)                                                                              ##STR12##                                        n =  2 abs 650 nm  n                                                          =  3 abs 760 nm          (13)                                                                              ##STR13##                                        abs 740 nm               (14)                                                                              ##STR14##                                        abs 780 nm               (15)                                                                              ##STR15##                                        abs 790 nm               (16)                                                                              ##STR16##                                        abs 745 nm               (17)                                                                              ##STR17##                                        abs 820 nm               (18)                                                                              ##STR18##                                                                 (19)                                                                              ##STR19##                                        R =  H                   (20)                                                                              ##STR20##                                                                 (21)                                                                              ##STR21##                                        abs 620 nm               (22)                                                                              ##STR22##                                        abs 580 nm               (23)                                                                             NdP.sub.5 O.sub.14                                                         (24)                                                                             LiNdP.sub.4 O.sub.12                                                       (25)                                                                             Na.sub.5 Nd(WO.sub.4).sub.4                                                (26)                                                                             Al.sub.3 Nd(BO.sub.3).sub.4                                                (27)                                                                             Cs.sub.2 NaNdCl.sub.6                                                      (28)                                                                             Li(Nd.sub.0.9 Yb.sub.0.1)P.sub.4 O.sub.12                                  (29)                                                                              ##STR23##                                        abs 655 nm               (30)                                                                              ##STR24##                                        abs 700 nm               (31)                                                                              ##STR25##                                        abs 640 nm               (32)                                                                              ##STR26##                                        abs 705 nm               (33)                                                                              ##STR27##                                        abs 810 nm               (34)                                                                              ##STR28##                                        abs 740 nm               (35)                                                                              ##STR29##                                        abs 790 nm               (36)                                                                              ##STR30##                                        abs 820 nm               (37)                                                                              ##STR31##                                        abs 930 nm               (38)                                                                              ##STR32##                                        abs 930 nm               (39)                                                                              ##STR33##                                        abs 1010 nm              (40)                                                                              ##STR34##                                        abs 1050 nm              (41)                                                                              ##STR35##                                        abs 470 nm               (42)                                                                              ##STR36##                                        abs 480 nm               (43)                                                                              ##STR37##                                        abs 495 nm               (44)                                                                              ##STR38##                                        abs 540 nm               (45)                                                                              ##STR39##                                        abs 570 nm               (46)                                                                              ##STR40##                                        abs 570 nm               (47)                                                                              ##STR41##                                        abs 570 nm               (48)                                                                              ##STR42##                                        abs 580 nm               (49)                                                                              ##STR43##                                        abs 610 nm               (50)                                                                              ##STR44##                                        abs 600 nm               (51)                                                                              ##STR45##                                        abs 610 nm               (52)                                                                              ##STR46##                                        abs 580 nm               (53)                                                                              ##STR47##                                        abs 615 nm               (54)                                                                              ##STR48##                                        abs 630 nm               (55)                                                                              ##STR49##                                        abs 645 nm               (56)                                                                              ##STR50##                                        abs 480 nm               (57)                                                                              ##STR51##                                        abs 830 nm               (58)                                                                              ##STR52##                                        abs 795 nm               (59)                                                                              ##STR53##                                        abs 1080 nm              (60)                                                                             Nichia Chemical Industry NP-870                   abs 250 nm               (61)                                                                             LiAlO.sub.2 : Fe.sup.3+                           abs 250                  __________________________________________________________________________                                                         nm                   

The material of a type in which the near infrared fluorescent coloringmaterial is dispersed or mixed in the binder may be used while beingcombined with a usual coloring material or pigment. It is preferablethat the usual coloring material or pigment to be used while beingcombined do not absorb the exciting wavelength for the near infraredfluorescent coloring material. If the exciting wavelength for the nearinfrared fluorescent coloring material or pigment is not included in thevisible ray region, covering with the usual coloring material or pigmentor white pigment is able to improve the confidentiality of the copyprevention function.

The region which has a higher reflectance as compared with thereflectance of the medium and arranged to be used to record anidentification mark having invisible information recorded forrecognizing bills, securities and notes and the like (copy inhibitedoriginal documents which are subjects of the forgery inhibition) andinhibiting copying of them is formed by dissolving or dispersing thecolor material or pigment which is absorbed in the infrared ray regionand by printing a predetermined pattern in the copy-inhibited originaldocument.

The near infrared fluorescent coloring material or pigment can be amaterial having the absorption wavelength peak in a region of 700 nm orlonger, preferably 750 nm or longer. Since the material having thefluorescent wavelength peak in a range of 700 nm or shorter can bevisually detected, the secrecy cannot satisfactorily be maintained. If amaterial having the fluorescent wavelength peak in a range of 1100 nm orlonger is used, sensitivity of a Si-type photo-detection device, such asa CCD, deteriorates. In this case, the identification mark cannotaccurately be judged. It is further preferable to employ a fluorescentcoloring material or pigment having the fluorescent wavelength peak in arange of 1000 nm or shorter. The material of a type in which the nearinfrared fluorescent coloring material is dispersed or mixed in thebinder may be used while being combined with a usual coloring materialor pigment. It is preferable that the near infrared fluorescent coloringmaterial do not absorb the exciting wavelength for the near infraredfluorescent coloring material. The inhibition of the absorption ofvisible rays enables covering and improves the confidentiality of thecopy inhibition function.

Specifically, the near infrared fluorescent coloring material or pigmentthat can be used is as follows. However, a material which can beabsorbed in the infrared region, which has a large absorptioncoefficient and which exhibits excellent weather and light resisntace.

Compounds (62) to (126)

The binder resin for use in the foregoing near infrared fluorescentcoloring material or pigment may be a urea resin, melamine resin, alkydresin, acryl resin, vinyl chloride resin, aromatic sulfonamide resin, ora benzoquanamine resin or their copolymer.

    __________________________________________________________________________    (62)                                                                              ##STR54##                                           .sub.max =  706                                                               nm                    (63)                                                                              ##STR55##                                           .sub.max =  791                                                               nm                    (64)                                                                              ##STR56##                                           .sub.max =  728                                                               nm                    (65)                                                                              ##STR57##                                           .sub.max =  820                                                               nm                    (66)                                                                              ##STR58##                                           .sub.max =  798                                                               nm                    (67)                                                                              ##STR59##                                           .sub.max =  773                                                               nm                    (68)                                                                              ##STR60##                                           .sub.max =  723                                                               nm                    (69)                                                                              ##STR61##                                           .sub.max =  816                                                               nm                    (70)                                                                              ##STR62##                                           .sub.max =  790                                                               nm                    (71)                                                                              ##STR63##                                           .sub.max =  800                                                               nm                    (72)                                                                              ##STR64##                                           .sub.max =  759                                                               nm                    (73)                                                                              ##STR65##                                           .sub.max =  796                                                               nm                    (74)                                                                              ##STR66##                                           .sub.max =  793                                                               nm                    (75)                                                                              ##STR67##                                           .sub.max =  801                                                               nm                    (76)                                                                              ##STR68##                                           .sub.max =  819                                                               nm                    (77)                                                                              ##STR69##                                           .sub.max =  769                                                               nm                    (78)                                                                              ##STR70##                                           .sub.max =  785                                                               nm                    (79)                                                                              ##STR71##                                           .sub.max =  778                                                               nm                    (80)                                                                              ##STR72##                                           .sub.max =  746                                                               nm                    (81)                                                                              ##STR73##                                           .sub.max =  743                                                               nm                    (82)                                                                              ##STR74##                                           .sub.max =  928                                                               nm                    (83)                                                                              ##STR75##                                           .sub.max =  816                                                               nm                    (84)                                                                              ##STR76##                                           .sub.max =  927                                                               nm                    (85)                                                                              ##STR77##                                           .sub.max =  1050                                                              nm                    (86)                                                                              ##STR78##                                           .sub.max =  1010                                                              nm                    (87)                                                                              ##STR79##                                           .sub.max =  787                                                               nm                    (88)                                                                              ##STR80##                                           .sub.max =  785                                                               nm                    (89)                                                                              ##STR81##                                           .sub.max =  794                                                               nm                    (90)                                                                              ##STR82##                                           .sub.max =  796                                                               nm                    (91)                                                                              ##STR83##                                           .sub.max =  766                                                               nm                    (92)                                                                              ##STR84##                                           .sub.max =  771                                                               nm                    (93)                                                                              ##STR85##                                           .sub.max =  790                                                               nm                    (94)                                                                              ##STR86##                                           .sub.max =  791                                                               nm                    (95)                                                                              ##STR87##                                           .sub.max =  831                                                               nm                    (96)                                                                              ##STR88##                                           .sub.max =  954                                                               nm                    (97)                                                                              ##STR89##                                           .sub.max =  838                                                               nm                    (98)                                                                              ##STR90##                                           .sub.max =  940                                                               nm                    (99)                                                                              ##STR91##                                           .sub.max =  805                                                               nm                    (100)                                                                             ##STR92##                                           .sub.max =  1060                                                              nm                    (101)                                                                             ##STR93##                                           .sub.max =  944                                                               nm                    (102)                                                                             ##STR94##                                           .sub.max =  807                                                               nm                    (103)                                                                             ##STR95##                                           .sub.max =  737                                                               nm                    (104)                                                                             ##STR96##                                           .sub.max =  775                                                               nm                    (105)                                                                             ##STR97##                                           .sub.max =  775                                                               nm                    (106)                                                                             ##STR98##                                           .sub.max =  1090                                                              nm                    (107)                                                                             ##STR99##                                           .sub.max =  1090                                                              nm                    (108)                                                                             ##STR100##                                          .sub.max =  750                                                               nm                        ##STR101##                                                                (109)                                                                             ##STR102##                                          .sub.max =  765                                                               nm                        ##STR103##                                                                (110)                                                                             ##STR104##                                          .sub.max =  750                                                               nm                        ##STR105##                                                                (111)                                                                             ##STR106##                                          .sub.max =  765                                                               nm                        ##STR107##                                                                (112)                                                                             ##STR108##                                          .sub.max =  790                                                               nm                        ##STR109##                                                                (113)                                                                             ##STR110##                                          .sub.max =  835                                                               nm                    (114)                                                                             ##STR111##                                          .sub.max =  840                                                               nm                    (115)                                                                             ##STR112##                                          .sub.max =  772                                                               nm                    (116)                                                                             ##STR113##                                          .sub.max =  771                                                               nm                    (117)                                                                             ##STR114##                                          .sub.max =  772                                                               nm                    (118)                                                                             ##STR115##                                          .sub.max =  850                                                               nm                    (119)                                                                             ##STR116##                                          .sub.max =  870                                                               nm                    (120)                                                                             ##STR117##                                          .sub.max =  875                                                               nm                    (121)                                                                             ##STR118##                                          .sub.max =  905                                                               nm                    (122)                                                                             ##STR119##                                          .sub.max =  858                                                               nm                    (123)                                                                             ##STR120##                                          .sub.max =  855                                                               nm                    (124)                                                                             ##STR121##                                          .sub.max =  1010                                                              nm                    (125)                                                                             ##STR122##                                          .sub.max =  770                                                               nm                    (126)                                                                             ##STR123##                                          .sub.max =  765       __________________________________________________________________________                                                            nm                

By using an ultraviolet absorber or an anti-oxidant in the resin, theweather resistance of the resin can be improved. The resin can bemanufactured by a block resin crushing method, emulsificationpolymerizing method or a resin precipitation method or the like.

The maximal wavelength of the fluorescent spectrum of the near infraredfluorescent coloring material or pigment and the maximal wavelength ofthe absorption spectrum of the near infrared fluorescent coloringmaterial must be the same. In usual, the difference between them is 100nm or shorter, more preferably 50 nm or shorter.

If the maximal wavelength of the fluorescent spectral and that of theabsorption spectral are different from each other by 100 nm or more, thetransmission wavelength region of the CCD for detecting the nearinfrared rays is enlarged excessively, causing the contrast to belowered undesirably.

FIG. 21 is a graph of a reflectance of a copying paper for a copyingmachine. Since the copying paper has a substantially constantreflectance in a range from 450 to 1200 nm, it is preferable to be usedas a medium in the present invention.

Although a copying machine will now be described as an example ofapplication of the detection apparatus of the present invention, thepresent invention is not limited to this. The present invention may, ofcourse, be applied to various apparatus, such as an image scanner.

FIG. 2 is a schematic view which illustrates the copying machineaccording to the present invention.

Referring to FIG. 2, reference numeral 201 represents an image scannerportion for reading an original document and performing a digital signalprocess. Reference numeral 200 represents a printer portion fortransmitting a full color image corresponding to the image of anoriginal document read by the image scanner 201 on to paper.

In the image scanner portion 201, reference numeral 202 represents athick plate for an original document for securing an original document204 placed on an original document retainer glass (hereinafter called aplaten) 203. The original document 204 is irradiated with light emittedfrom a halogen lamp 205. Light reflected by the original document 204 isintroduced by mirrors 206 and 207 so that an image is, by a lens 208,formed on a four-line sensor (hereinafter called a "CCD") composed offour line CCD line sensors. The CCD 210 decomposes the color of opticalinformation of the original document to transmit, to a signal processingportion 209, red (R), green (G) and blue (B) components of full colorinformation and infrared ray information (IR) component. The elements205 and 206 are moved mechanically at speed v and the element 207 ismoved also mechanically at speed 1/2v in a vertical direction(hereinafter a "sub-scan direction") with respect to the electrical scandirection (hereinafter called a "main scan direction") of the linesensor so that the overall surface of the original document is scanned.

Reference numeral 211 represents a standard white plate for generatingdata for correcting read data corresponding to the line sensors 210-1 to210-4 for IR, R, G and B components when shading correction isperformed.

The standard white plate has substantially uniform reflectingcharacteristics with respect to visible rays to infrared rays as shownin FIG. 8, the standard white plate being white with respect to visiblerays.

The standard white plate is used to correct data transmitted from the IRsensor 210-1 with respect to infrared rays and data transmitted from theR, G, and B visible-ray sensors 210-2 to 210-4.

The signal processing portion 209 electrically processes the read signalto decompose the signal into magenta (M), cyan (C), yellow (Y) and black(BK) components which are then transmitted to the printer portion 200.One of the M, C, Y and BK components is plane-sequentially transmittedto the printer 200 whenever the image scanner portion 201 scans theoriginal document. When the original document has been scanned fourtimes, a color image can be formed.

The M, C, Y and BK image signals transmitted from the image scannerportion 201 are transmitted to a laser driver 212. The laser driver 212modulates and operates a semiconductor laser 213 in response to theimage signals. Laser beams are allowed to pass through a polygonalmirror 214, a f-θ lens 215, and the mirror 216 as to scan the surface ofa photosensitive drum 217.

Reference numerals 219 to 222 represent developing units comprising amagenta developing unit 219, a cyan developing unit 220, a yellowdeveloping unit 221 and a black developing unit 222. The four developingunits 219 to 222 alternately come in contact with the photosensitivedrum so that M, C, Y and BK electrostatic latent images formed on thephotosensitive drum 217 are developed by corresponding toners.

Reference numeral 223 represents a transfer drum for winding papersupplied from a paper cassette 224 or 225 around a transfer drum 223 totransfer a toner image developed on the photosensitive drum 217 on tothe paper.

Thus, the four colors, that is, M, C, Y and BK are sequentiallytransferred, and then the paper is allowed to pass through a fixing unit226 before it is discharged.

The halogen lamp 205 is commonly used to read visible ray informationand to read infrared ray information, the halogen lamp 205 having bothirradiation wavelength components required to read the two types ofinformation items. By using the common irradiation system as describedabove, irradiation light beams having different wavelength componentsfor reading visible and infrared rays information are effectivelyapplied to the original document.

FIG. 7A illustrates the structure of the CCD 210 for use in thisembodiment.

Referring to FIG. 7A, reference numeral 210-1 represents a lightreceiving device array for reading infrared ray (IR), and 210-2, 210-3and 210-4 represent light receiving device arrays for respectivelyreading R, G and B wavelength components.

The IR, R, G and B sensors 210-1 to 210-4 respectively have openingshaving a diameter of 10 lm in the main scan direction and the sub-scandirection.

The four light receiving device arrays having different opticalcharacteristics are disposed on the same silicon chip in a monolithicmanner so that the IR, R, G and B sensors are disposed in parallel toeach other to read the same line of the original document.

By using the CCD constituted as described above, the common opticalsystem, such as the lens, can be used to read the visible rays andinfrared rays.

As a result, accuracy in the optical adjustment can be improved and theadjustment can easily be completed.

Reference numeral 210-5 represents a glass plate having a characteristiccapable of cutting infrared rays in the diagonal line section thereof,the glass plate 210-5 having a thickness of about 300 μm.

The characteristic of cutting infrared rays is realized in the diagonalline section due to a diachronic mirror 210-11. The characteristic ofcutting infrared rays is shown in FIG. 11.

The glass plate is bonded to the surface of the chip in such a mannerthat the evaporated surface of the glass plate faces the sensor side.

FIG. 7B is an enlarged view which illustrates the light receivingdevice. Each sensor has a length of 10 μm per length in the main scandirection. Each sensor includes 5,000 pixels in the main scan directionas to read the shorter side direction (297 mm) of an A3-size originaldocument at a resolving power of 40 dpi. The R, G and B sensors aredisposed at a line interval of 80 μm while being disposed at each 8lines when the resolving power in the sub-scan direction is 400 lpi(line per inch).

The line interval between the IR sensor 210-1 and the R sensor 210-2 ismade to be 160 μm (16 lines) which is twice the other line interval. Asa result of the foregoing structure in which the interval between the IRsensor 210-1 and the R sensor 210-2 is made to be longer than theinterval between the other sensors, the evaporated surface 210-11 of theglass plate 210-5 can be made to face the sensors 210-2 to 210-4 whilemaking the non-evaporated portion to face the sensor 210-1 at a lowfastening position accuracy at the time of bonding the glass plate 210-5to the surface of the chip.

The glass plate 210-5 is fastened adjacent to the sensor surface, whilethe evaporated film 210-11 for blocking infrared rays is fastened toface the sensor. The reason for this is that light beams passing towardthe sensor are converged by the lens 209 and therefore the light beamspassing toward the sensors are superposed at a position distant from thesurface of the sensor as shown in FIG. 13. That is, if the infrared raycutting filter 210-11 is made to filter only light beams passing towardthe sensors 210-2 to 210-4, the infrared ray cutting filter 210-11 mustbe fastened to a position adjacent to the sensor at which the IR lightbeam and the R light beam are not, superposed.

The arrangement made in such a manner that the infrared ray cuttingfilter 210-11 is disposed adjacent to the surface of the sensor enablesthe allowable width a for fitting the IR filter between the IR lightbeams and the R light beams to be widened. Therefore, the accuracy forfitting the glass plate 210-13 to the sensor chip can be lowered.

If the infrared ray cutting filter is fastened to the surface of theglass plate 210-5 opposing the sensor, the IR light beams and the Rlight beams are superposed. As a result, if the infrared ray cuttingfilter is disposed to sufficiently filter the R light beams, a majorportion of the IR light beams focused on to the IR sensor 210-1 isundesirably cut, causing the level of the IR signal to be loweredexcessively.

As an alternative to the structure in which the glass plate 210-5 isfastened as shown in FIG. 14, the infrared ray cutting filter 210-11 maybe disposed on the surface of the cover glass 210-13 facing the sensor.In this case, the distance d from the surface of the sensor to theinternal surface of the cover glass must sufficiently be shortened byconstituting a ceramic package 210-12 of the CCD sensor so that theinfrared ray cutting filter 210-11 disposed on the internal surface ofthe cover glass does not substantially interrupt the IR light beams.

With reference to FIG. 10, the filter spectrum characteristic of the IR,R, G and B line sensors of the CCD 210 will now be described.

The characteristics R has sensitivity with respect to light beams in thered wavelength region and the infrared ray wavelength region. Thecharacteristics G has sensitivity with respect to light beams in thegreen wavelength region and the infrared wavelength region. Thecharacteristics B has sensitivity with respect to light beams in theblue wavelength region and the infrared wavelength region.

Since filters 210-6 and 210-7 are superposed on the IR sensor 210-1, theIR sensor 210-1 has sensitivity with respect to infrared light beamsrepresented by the diagonal lines shown in FIG. 10.

As can be understood from FIG. 10, the R, G and B filters 210-8 to210-10 have sensitivity with respect to infrared rays in a range of 700nm or longer. Therefore, the infrared ray cutting filter 210-11 hascharacteristics shown in FIG. 11.

FIG. 9 shows spectrum absorption ratio of an infrared ray absorberSIR-159 manufactured by Mitsui Toatsu for used to form a detection markof a specific original document according to this embodiment. Thisembodiment is arranged in such a manner that the presence of theinfrared ray absorber is read by the IR sensor that is arranged todetect only infrared rays ranging from 750 nm to 850 nm.

In order to achieve this, a far infrared ray cutting filter of adiachronic mirror as shown in FIG. 12 is disposed on the lens 209. Sincethe foregoing filter does not adversely affect the R, G and B sensors210-2 to 210-4 as well as the IR sensor 210-1, it is disposed in thelens portion commonly provided for the visible rays and infrared rays.As a result, the filter to be fastened to the lens 209 can be designedto simply have the far infrared ray cutting characteristics. Therefore,excellent far infrared ray cutting characteristics can be realized by asimple interference film structure.

FIGS. 15A and 15B are block diagrams which illustrates the flow of animage signal in the image scanner portion 201. The image signaltransmitted from the CCD 210 is received by an analog signal processingportion 3001 as to be subjected to a gain adjustment and an offsetadjustment, and then converted by A/D converters 3002 to 3005 into 8-bitdigital image signals for each color signal. Then, the image signal issupplied to shading correction portions 3006 to 3009 as to be subjectedto a known shading correction using a read signal of the standard whileplate 211 for each color.

Reference numeral 3019 represents a clock generating portion forgenerating clocks in a pixel unit. Reference numeral 3020 represents aline counter for counting clocks to generate a pixel address output forone line. Reference numeral 3021 represents a decoder for decoding mainscan address supplied from the main scan address counter 3020 togenerate CCD drive signals, such as shift pulses and reset pulses, VEsignals representing an effective region in a read signal for one linesupplied from the CCD, and a line synchronizing signal HSYNC. Thecounter 3020 is cleared in response to the HSYNC signal to startcounting the main scan address of the next line.

Since the light receiving portions 210-1, 210-2, 210-3 and 210-4 of theCCD 210 are disposed while having predetermined intervals, the spatialdeviation in the sub-scan direction is corrected in line delay devices3010, 3011 and 3012. Specifically, the IR, R, and G signals for readinginformation about the original document in the sub-scan direction withrespect to the B signal are line-delayed in the sub-scan direction to bemade coincide with the B signal.

Reference numerals 3013, 3014 and 3015 represent light quantity/densityconversion portion each comprising a look up table ROM to convert R, Gand B brightness signals into C, M and Y density signals. Referencenumeral 3016 represents a known masking and UCR circuit which receivesthree primary color signals Y, M and C to sequentially transmit Y, M, Cand Bk signals while having a predetermined bit length, for example, 8bits whenever a reading operation is performed.

Reference numeral 3 represents an identifying portion for detecting aspecific pattern in the original document which is the characteristic ofthe present invention.

Reference numeral 3018 represents a CPU portion for controlling anoptical system for reading the original document, controlling thesequence for controlling the operation for turning on/off an originaldocument irradiation lamp 205 and generating a pixel region signal VSYNCin the sub-scanning direction. In accordance with the result of judgmentsupplied from the recognition portion 3, the CPU portion 3018 controls aselector 3017 to transmit, to the printer, a port output in place of theread signal to inhibit the operation of copying the specific originaldocument.

FIG. 16 shows timings of the respective control signals.

The VSYNC signal is an image effective region signal in the sub-scandirection as to be used to form sequential output signals (M), (C), (Y)and (Bk) with which the image is read in a region of "1". The VE signalis an image effective region signal in the main scan direction toarrange the balance of the main scan start position in the region of"1". The CLOCK signal is a pixel synchronizing signal which transfersimage data at the first transition timing 0→1.

The image pattern to be detected in the present invention will now bedescribed with reference to FIGS. 1A and 1B. FIGS. 1A and 1B illustratenear infrared fluorescent coloring materials which do not absorb visiblerays having the characteristics shown in FIG. 9 is used together with acoloring material which absorbs about 600 nm to record low reflectanceportions 101.

Near infrared fluorescent coloring material having characteristics shownin FIG. 20A is used in high reflectance portions 102. Since the highreflectance portions 102 are printed as small patterns in the form ofsquares each having a side of about 12.0 μm and they are substantiallythe same color in the visible region, the image pattern shown in FIGS.1A and 1B cannot be identified visually. However, it can be detected inan infrared region. Although a pattern in the form of a square having aside of about 120 μm is described as an example to make ensuingdescriptions, the foregoing region has a size of about four pixels ifthe same is read at 400 dpi (dot per inch). It should be noted that themethod of forming the pattern is not limited to the foregoing method.

With reference to FIG. 4, the identifying portion shown in FIGS. 15A and15B will now be described. Reference numerals 10-1 to 10-4 shown in FIG.4 represent image data line delay portions each comprising a FIFO. Anaddress pointer is initialized in response to a line synchronizingsignal HSYNC (omitted from illustration), while data is written or readfor pixel unit in response to the CLOCK signal. Each of the image dataline delay portions 10-1 to 10-4 delay R, G, B and IR data of 32 bits byone line.

First, an input signal is held in flip flops 11-1 and 11-2 to be delayedfor two pixels to generate data for pixel A. Further, the line memories10-1 and 10-2 delay the data for two lines to generate data for pixel C.Data items for the pixel C respectively are delayed by two pixels andfour pixels to generate data about subject pixel data X and data aboutpixel B. Similarly, data about pixel D is supplied to a judging portion12.

The position relationship among the pixels A, B, C and D around thesubject pixel X is as shown in FIG. 5.

That is, if the subject pixel X is reading the low reflectance portion101 shown in FIGS. 1A and 1B, the pixels Ar Bo C and D are reading thepixels of the patterns positioned around the low reflectance portion101.

A judgment algorithm set to the judging portion 12 according to thisembodiment will now be described.

Assuming that R, G, B and IR components of the reading signal whichforms the pixel signal for A are AR, AG, AB and AIR and pixels signalsfor B, C and D are defined, average values YR, YG, YB and YIR of theread signals for each color component R, G, B and IR in each pixelsignal are defined by the following equations:

    Y.sub.R =1/4(A.sub.R +B.sub.R +C.sub.R +D.sub.R)

    Y.sub.G =1/4(A.sub.G +B.sub.G +C.sub.G +D.sub.G)

    Y.sub.B =1/4(A.sub.B +B.sub.B +C.sub.B +D.sub.B)

    Y.sub.IR =1/4(A.sub.IR +B.sub.IR +C.sub.IR +D.sub.IR)

An aimed pattern is judged in accordance with the difference betweenaverage value Y obtained by the foregoing equation and the subject pixelX.

That is, assuming that the R, G, B and IR components of X are XR, XG, XBand XIR respectively, the following relationships are held:

    ΔR=|Y.sub.R -X.sub.R |

    ΔG=|Y.sub.G -X.sub.G |

    ΔB=|Y.sub.B -X.sub.B |

    ΔIR=|Y.sub.IR -X.sub.IR |

If the following relationships are held, a judgment is made that apattern is present:

    ΔR<K and

    ΔG<K and

    ΔB<K and

    ΔIR>L1 or Y.sub.IR /X.sub.IR >L2

where K, L1 and L2 are constants.

That is, if the color tone is not considerably different in the visibleregion (smaller than K) between the subject pixel X and the adjacentpixels A, B, and C and D and if the difference is larger by the constantL1 in the infrared region, or if the ratio of the level of the subjectpixel X and that of the adjacent pixels is larger than the constant L1,a judgment is made that a specific pattern is present.

The reason why the ratio is used to make the judgment as well as thejudgment of the infrared region is that the deterioration in theinfrared ray signal level due to contamination of the original documentmust be compensated. In this embodiment, the overall damping of theinfrared ray read signal due to the influence of contamination iscompensated by detecting the ratio.

If the high reflectance portion 102 recorded with ink containing thenear infrared fluorescent coloring material is present adjacent to thesubject pixel X, the level difference for use in the judgment is furtherenlarged. Therefore, erroneous recognition can be prevented.

When reading operations 103, 104 and 105 are performed in different scandirections as shown in FIG. 1A, the intensities of the IR signalsrespectively are as shown in FIG. 1B so that the low reflectanceportion, the reflectance portion of the medium and the high reflectanceportion are detected. Therefore, the recognition rate can be improvedwhile performing together the foregoing judgment.

If a near infrared ray absorbing film is used to prevent the judgment,the overall IR intensity is lowered so that the abnormality can bejudged.

If a near infrared ray reflecting film is used to prevent the judgment,the abnormality can be judged because the overall IR intensity isexcessively high.

If an intermediate-density infrared ray absorbing film or an infraredray reflecting film is used, the IR intensity of the medium is simplychanged, and therefore the judgment can be performed normally.

FIG. 6 illustrates the structure of the judgment portion 12 adapted tothe foregoing algorithm.

An adder 121 simply adds the color components for four pixels totransmit the upper eight bits to obtain YR, YG, YB and YIR. A subtractor122 obtains the difference from each component of the subject pixelsignal to supply upper five bits of the components ΔR, ΔG and ΔB to ajudgment LUT 128 comprising a ROM. If each of the upper five bits issmaller than constant K, 1 is transmitted from the LUT 128.

Similarly, 8-bit YIR and XIR are supplied to an address terminal of ajudgment LUT comprising a ROM in a case of an infrared read signal. Ifthe judgment ΔIR>L1 or YIR/XIR>L2 is resulted in the foregoingcalculation ΔIR=YIR-XIR, 1 is transmitted from the LUT 129.

The logical product of the output from each LUT is calculated in an ANDgate 130, and therefore a pattern can be detected if 1 is obtained atthe output terminal of the AND gate 130.

The result of the judgment is supplied to a latch 3022 shown in FIGS.15A and 15B. The latch output is supplied to an input port P10 of a CPU3018 so that the CPU recognizes the detection of the specific mark. TheCPU clears the latch 3022 in response to a signal of an output port P9prior to starting the copying sequence to prepare for the next patterndetection.

A usual copying operation and an operation of the CPU to control theoperation of judging the recognition mark will now be described withreference to FIG. 17.

When an operator places the original document 204 on the platen 203 andstarts the copying operation by operating a control portion (omittedfrom illustration), the CPU 3018 controls a motor (omitted fromillustration) to move the reflecting mirror 206 to a position below thestandard white plate 211.

Then, the halogen lamp 205 is lit on to irradiate the standard whiteplate 211 so that the shading correction portions 3006 to 3009 sampleshading data for the IR, R, G and B signals (step 1).

Then, the port output P9 is made to be zero, the output from the latch3022 is made to be zero-cleared, the output from P8 is made to be zero,input A of the selector 3017 is selected so that a masked andUCR-processed image signal is supplied to the printer. Then, the outputfrom P9 is made to be 1, and the clearing operation of the latch 3022 iscompleted (step 2).

Then, the original document is read four times to correspond to theoperation of recording the four colors M, C, Y and BK performed in theprinter portion so that the image is recorded. Further, the recognitionmark is detected, and the recording operation is controlled inaccordance with the result of the detection.

First, a magenta image is recorded in such a manner that the CPUqualifies the processing condition for processing the magenta image tobe performed by the masking and UCR processing portion to cause theoptical system to perform the scanning operation and to supply a magentasignal to the printer. After the scanning operation has been completed,the CPU returns the optical system to the scan start position (step 3).

The CPU periodically reads the port 10 during the operation of readingthe original document to judge whether or not the input to the port 10is 1. If the P10 is 1, a judgment is made that a specific originaldocument, the normal reproduction of which must not be inhibited, isbeing copied, and the outputs from P0 to P7 are made to be FFH in step7. Further, the output from P8 is made to be 1 to transmit a solidsignal FFH to the printer to inhibit the normal copying operation.

Similarly, recording of cyan, yellow and black data is controlled insteps 4 to 6, and the CPU periodically examines the state of P10. If theoutput from P10 is 1, full black FFH data is transmitted to the printerin step 7.

If P10=1 is detected during the operation of recording the cyan data,the magenta data is normally copied. However, all of cyan, yellow andblack data items are recorded in the form of solid FFH data.

Second Embodiment

FIGS. 18A and 18B illustrate an example of a second structure of animage reading apparatus according to the present invention.

A CCD is, as shown in FIG. 18A, is arranged in such a manner thattwo-line sensors are formed on a common silicon chip in a monolithicmanner.

A line sensor 3301-1 is an infrared ray reading sensor (an IR sensor),and a line sensor 3301-2 is a full color line sensor in which R, G and Bsensors are alternately disposed in pixel units.

A glass plate 3301-5 having a dichroic filter 3301-11 for cuttinginfrared rays evaporated thereof is fastened on to the foregoing sensorby a method similar to that shown in FIGS. 7A and 7B.

The dichroic filter 3301-11 has the infrared ray cutting characteristicsshown in FIG. 11 similarly to 210-11.

The glass plate is fastened to the CCD chip similarly to the methodshown in FIGS. 7A and 7B such that the end of the evaporated portion ispositioned between the line sensors 3301-1 and 3301-2.

FIG. 18B is an enlarged view which illustrates pixels of the linesensors 3301-1 and 3301-2.

The IR sensor 3301-1 has a pixel size 18 μm×18 μm and in which R and Bfilters having characteristics shown in FIG. 10 are superposed on thesensor, the IR sensor 3301-1 having the infrared ray transmissioncharacteristics of the IR sensor 210-1.

By combining the IR sensor 3301-1 with a far infrared ray cutting filterdisposed in the imaging optical system similar to that according to thefirst embodiment and having the characteristics shown in FIG. 12,infrared ray reading characteristics similar to that according to thefirst embodiment are attained.

Reference numeral 3301-2 represents R, G and B sensor arrays positionedaway from the IR sensor by 180 μm (for 10 lines), the sensor array3301-2 having an arrangement in which R, G and B pixels having a size of6 μm to correspond to the size of 18 mm of one pixel of the IR sensor inthe main scan direction. Each of the R, G and B pixels is provided witha color decomposing filter having the characteristics shown in FIG. 10.

The sensor according to this embodiment has 5,000 pixels in the mainscan direction to read an A3-size original document at 400 dpi, and5,000 combinations of R, G and B are provided.

In order to project the size 63.5 μm (one pixel of 400 dpi) of theoriginal document retainer onto a size of 18.5 μm, the contraction ratioof the optical system is made to be 18.5/63.5.

When the identification pattern according to the first embodiment wasmeasured by the foregoing detection apparatus, an excellent judgment wasperformed.

Third Embodiment

FIGS. 19A and 19B illustrate an example of the structure of a thirdembodiment of the image reading apparatus according to the presentinvention.

A CCD 3401 comprises a sensor 3402 having R, G, B and IR pixels formedon lines as shown in FIG. 18A so that image data for one pixel iscolor-decomposed (the wavelength is decomposed) by the combination ofIR, R, G and B to read the image data.

Each of the IR, R, G and B pixels has a size of 63.5/4 μm in the mainscan direction so that a pixel of 63.5 μm is read by a combination ofIR, R, G and B.

Since the sensor according to this embodiment reads an original documentat 400 dpi, the contraction ratio of an optical system is made to be onetime so that the size 63.5 μm (one pixel of 400 dpi) of the originaldocument retainer is projected onto the size of 63.5 μm.

The IR reading pixel has R and B filters having the characteristicsshown in FIG. 10 and superposed on the sensor to have the infrared raytransmission characteristics of the IR sensor 210-1.

By combining it with the far infrared ray cutting filter disposed in theimaging optical system (omitted from illustration) and having thecharacteristics shown in FIG. 12, the infrared ray readingcharacteristics similar to that obtainable from that according to thefirst embodiment can be attained. The R, G and B reading pixels havecolor decomposing filters having the characteristics shown in FIG. 10.

A glass plate 3403 having dichroic filters 3403-11 for cutting infraredrays, evaporated at a pitch of 63.5 μm and having a width of 63.5/4 μmis fastened on the sensor as shown in FIG. 19A.

The dichroic filter 3404 has the infrared ray cutting characteristicssimilarly to 210-11.

The glass plate is fastened to the CCD chip similarly to that shown inFIGS. 7A and 7B in such a manner that its evaporated side faces thesurface of the chip and the portion, which is not evaporated,corresponds to the IR pixels as shown in FIGS. 19A and 19B.

When the identification pattern according to the first embodiment wasmeasured with the foregoing detection apparatus, an excellent judgmentwas performed.

Although the third embodiment is arranged in such a manner that the IR,R, G and B pixels for reading one pixel are arranged in the main scandirection, another structure may be employed which is arranged in such amanner that they are disposed in a 2D manner and the infrared raycutting dichroic filters are disposed in only the portions of the glassplate that correspond to the R, G and B pixels.

Although the foregoing embodiment is arranged in such a manner that theinfrared ray cutting filter is made of transparent material and it isfastened to the sensor, the filter is not limited to the infrared raycutting filter. The filter may be a filter for cutting ultraviolet raysthat are not required to read visible information.

As described above, use of the invisible information recorded mediumhaving the identification mark composed of a region having a highreflectance and a region having a low reflectance region as comparedwith the reflectance of the medium at the same near infrared raywavelength and an apparatus for detecting the invisible informationrecording medium enables the specific original document to be judgedassuredly while reducing the cost.

Further, an attempt of judgment prevention using the infrared rayabsorbing film or an infrared reflecting film can assuredly be judged.

Fourth Embodiment

This embodiment is arranged in such a manner that an invisibleinformation recording medium is used which serves as a recording mediumfor inhibiting copying and reading, having no information recorded inthe visible ray region thereof and having an identification mark whichabsorbs near infrared rays so that inhibition of copying and reading isidentified.

The invisible information recording medium according to this embodimentand having visible information comprises the identification markrepresenting the copying and reading inhibition so that copying andreading are inhibited when the mark is detected.

The identification mark having the invisible information for inhibitingcopying is recorded in such a manner that coloring material or pigmentwhich does not absorb visible rays and which absorbs near infrared raysis dissolved or dispersed in a binder and a predetermined pattern is, byprinting or the like, formed in the recording medium for inhibitingcopying.

The near infrared ray absorbing coloring material or pigment may be amaterial having the absorption wavelength peak in a range of 700 nm orlonger, preferably 750 nm or longer. Since the material having theabsorption wavelength peak in a range of 700 nm or shorter can bevisually detected, the secrecy cannot satisfactorily be maintained. If amaterial having the absorption wavelength peak in a range of 1100 nm orlonger is used, sensitivity of a Si-type photo-detection device, such asa CCD, deteriorates. In this case, the identification mark cannotaccurately be judged. It is further preferable to employ a coloringmaterial or pigment having the absorption wavelength peak in a range of1000 nm or shorter.

The foregoing near infrared ray absorbing coloring material or pigmentmay be dispersed or mixed with the binder while being combined with anultraviolet absorber or an antioxidant.

The near infrared ray absorbing coloring material or pigment must be atype that does not absorb visible rays. The absorbance of the maximumabsorbing wavelength in the infrared ray region must be 5 times or morethe absorbance of the maximum absorbing wavelength, more preferably 10times or more. If it is 5 times or less, it can easily visiblyrecognized in a visible ray region if the mark in the near infrared rayregion is allowed to have a thickness that can be identified. Therefore,an adverse influence is resulted on the information to be recorded.

More specifically, any one of the following near infrared ray absorbingcoloring material or pigment may be used. However, a material may beused regardless of the exemplified materials if it absorbs near infraredrays and exhibits large absorbance and excellent weathering and lightresistance.

Compounds (1) to (44)

The binder resin for use in the foregoing near infrared ray absorbingcoloring material or pigment may be a urea resin, melamine resin, alkydresin, acryl resin, vinyl chloride resin, aromatic sulfonamide resin, ora benzoquanamine resin or their copolymer.

    __________________________________________________________________________    (1)                                                                               ##STR124##                                          .sub.max =  820                                                               nm                    (2)                                                                               ##STR125##                                          .sub.max =  798                                                               nm                    (3)                                                                               ##STR126##                                          .sub.max =  773                                                               nm                    (4)                                                                               ##STR127##                                          .sub.max =  790                                                               nm                    (5)                                                                               ##STR128##                                          .sub.max =  800                                                               nm                    (6)                                                                               ##STR129##                                          .sub.max =  796                                                               nm                    (7)                                                                               ##STR130##                                          .sub.max =  793                                                               nm                    (8)                                                                               ##STR131##                                          .sub.max =  801                                                               nm                    (9)                                                                               ##STR132##                                          .sub.max =  819                                                               nm                    (10)                                                                              ##STR133##                                          .sub.max =  769                                                               nm                    (11)                                                                              ##STR134##                                          .sub.max =  785                                                               nm                    (12)                                                                              ##STR135##                                          .sub.max =  778                                                               nm                    (13)                                                                              ##STR136##                                          .sub.max =  928                                                               nm                    (14)                                                                              ##STR137##                                          .sub.max =  816                                                               nm                    (15)                                                                              ##STR138##                                          .sub.max =  927                                                               nm                    (16)                                                                              ##STR139##                                          .sub.max =  1050                                                              nm                    (17)                                                                              ##STR140##                                          .sub.max =  1010                                                              nm                    (18)                                                                              ##STR141##                                          .sub.max =  787                                                               nm                    (19)                                                                              ##STR142##                                          .sub.max =  785                                                               nm                    (20)                                                                              ##STR143##                                          .sub.max =  794                                                               nm                    (21)                                                                              ##STR144##                                          .sub.max =  796                                                               nm                    (22)                                                                              ##STR145##                                          .sub.max =  771                                                               nm                    (23)                                                                              ##STR146##                                          .sub.max =  790                                                               nm                    (24)                                                                              ##STR147##                                          .sub.max =  831                                                               nm                    (25)                                                                              ##STR148##                                          .sub.max =  940                                                               nm                    (26)                                                                              ##STR149##                                          .sub.max =  805                                                               nm                    (27)                                                                              ##STR150##                                          .sub.max =  1060                                                              nm                    (28)                                                                              ##STR151##                                          .sub.max =  944                                                               nm                    (29)                                                                              ##STR152##                                          .sub.max =  954                                                               nm                    (30)                                                                              ##STR153##                                          .sub.max =  1090                                                              nm                    (31)                                                                              ##STR154##                                          .sub.max =  1090                                                              nm                    (32)                                                                              ##STR155##                                          .sub.max =  840                                                               nm                    (33)                                                                              ##STR156##                                          .sub.max =  772                                                               nm                    (34)                                                                              ##STR157##                                          .sub.max =  765                                                               nm                        ##STR158##                                                                (35)                                                                              ##STR159##                                          .sub.max =  790                                                               nm                        ##STR160##                                                                (36)                                                                              ##STR161##                                          .sub.max =  835                                                               nm                    (37)                                                                              ##STR162##                                          .sub.max =  858                                                               nm                    (38)                                                                              ##STR163##                                          .sub.max =  855                                                               nm                    (39)                                                                              ##STR164##                                          .sub.max =  1010                                                              nm                    (40)                                                                              ##STR165##                                          .sub.max =  770                                                               nm                    (41)                                                                              ##STR166##                                          .sub.max =  765                                                               nm                    (42)                                                                              ##STR167##                                          .sub.max =  870                                                               nm                    (43)                                                                              ##STR168##                                          .sub.max =  875                                                               nm                    (44)                                                                              ##STR169##                                          .sub.max =  905       __________________________________________________________________________                                                            nm                

As another example of the identification mark having invisibleinformation for inhibiting copying, fluorescent coloring material orpigment which does not absorb the visible rays but which has fluorescentcharacteristics in the near infrared ray region is dissolved ordispersed in the binder and a predetermined pattern is, by printing orthe like, formed on the recording medium for inhibiting copying.

The fluorescent coloring material or pigment may be a material havingthe fluorescent wavelength peak in a range of 700 nm or longer,preferably 800 nm or longer.

Since the material having the fluorescent wavelength peak in a range of700 nm or shorter can be visually detected, the secrecy cannotsatisfactorily be maintained. If a material having the fluorescentwavelength peak in a range of 1100 nm or longer is used, sensitivity ofa Si-type photo-detection device, such as a CCD, deteriorates. In thiscase, the identification mark cannot accurately be judged. It is furtherpreferable to employ a fluorescent coloring material or pigment havingthe fluorescent wavelength peak in a range of 1000 nm or shorter. Sincethe near infrared fluorescent rays can be detected when they areseparated from exciting rays, it is preferable that the two types of therays have wavelengths which are considerably different from each other.Therefore, near infrared fluorescent coloring material or pigment andexciting rays are selected such that they are different from each otherby 50 nm or more, preferably 100 nm or more.

If the absorption of exciting rays takes place in the visible region, itcan be recognized visually and information to be recorded is adverselyaffected. It is preferable to employ the exciting rays having theabsorption wavelength peak of 750 nm or longer.

The exciting wavelength is selected depending upon the type of the lightsource and the spectrum filter. The near infrared fluorescent coloringmaterial may be a xanthene, oxazine, thiazine, polymethine or strylcompound. As an inorganic compound, a solid laser material of a typecontaining a rare earth element is used.

More specifically, any one of the following near infrared fluorescentcoloring material may be used. However, a material may be usedregardless of the exemplified materials if it has fluorescent rays inthe near infrared ray region and exhibits excellent fluorescent quantumyield, weather and light resistance.

Compounds (45) to (65)

The binder resin for use in the foregoing near infrared fluorescentcoloring material or pigment may be a urea resin, melamine resin, alkydresin, acryl resin, vinyl chloride resin, aromatic sulfonamide resin, ora benzoquanamine resin or their copolymer. By using a ultravioletabsorber or an anti-oxidant with the foregoing resin, the lightresistance of the resin can be improved. The binder resin can bemanufactured by a block resin crushing method, emulsificationpolymerizing method or a resin precipitation method or the like.

    __________________________________________________________________________    (45)                                                                              ##STR170##                                           abs 780 nm           (46)                                                                              ##STR171##                                           abs 790 nm           (47)                                                                              ##STR172##                                           abs 820 nm           (48)                                                                              ##STR173##                                                                (49)                                                                              ##STR174##                                           R =  H               (50)                                                                              ##STR175##                                                                (51)                                                                             NdP.sub.5 O.sub.14                                                         (52)                                                                             LiNdP.sub.4 O.sub.12                                                       (53)                                                                             Na.sub.5 Nd(WO.sub.4).sub.4                                                (54)                                                                             Al.sub.3 Nd(BO.sub.3).sub.4                                                (55)                                                                             Cs.sub.2 NaNdCl.sub.6                                                      (56)                                                                             Li(Nd.sub.0.9 Yb.sub.0.1)P.sub.4 O.sub.12                                  (57)                                                                              ##STR176##                                           abs 930 nm           (58)                                                                              ##STR177##                                           abs 930 nm           (59)                                                                              ##STR178##                                           abs 1010 nm          (60)                                                                              ##STR179##                                           abs 1050 nm          (61)                                                                             Nichira Chemical Industry NP-870                      abs 250 nm           (62)                                                                             LiAlO.sub.2 :Fe.sup.3+                                abs 250 nm           (63)                                                                              ##STR180##                                           abs 830 nm           (64)                                                                              ##STR181##                                           abs 795 nm           (65)                                                                              ##STR182##                                           abs 1080             __________________________________________________________________________                                                             nm               

FIG. 21 illustrates reflection spectrum of copying paper for a copyingmachine as an example of a recording medium in a state prior torecording the identification mark. Since the copying paper has asubstantially constant reflectance in a range from 450 to 1200 nm, it ispreferable to be used as a medium in the present invention.

Since the usual paper, such as the copying paper, has a relatively highreflectance, change due to absorption is suitable as the change in thereflectance utilized as the identification mark according to the presentinvention.

In case where fluorescent rays are used, the absorption wavelength foruse as the excitement ray is usually shorter than the fluorescentwavelength. Therefore, the visible region is easily affected. If thewavelength is lengthened to prevent the influence upon the visibleportion, the fluorescent wavelength is further lengthened. Therefore,the structure of the optical system becomes difficult to be formed.

An image pattern to be detected and according to the present inventionwill now be described with reference to FIG. 3. FIG. 3 illustrates a lowreflection portion 101 recorded by using ink formed by dissolving, in aPMMA, infrared absorption coloring material which has thecharacteristics shown in FIG. 9 and which is not absorbed in the visibleportion.

Since the image patterns are printed as small patterns in the form ofsquares each having a side of about 120 μm and they are substantiallythe same color in the visible region, the image pattern shown in FIG. 3cannot be identified visually. However, it can be detected in aninfrared region. Although a pattern in the form of a square having aside of about 120 μm is described as an example to make ensuingdescriptions, the foregoing region has a size of about four pixels ifthe region b is read at 400 dpi (dot per inch). It should be noted thatthe method of forming the pattern is not limited to the foregoingmethod.

If an attempt is made to prevent the judgment by forming an infrared rayabsorbing film in order to copy an original document recorded by using arecording medium having the identification mark according to the presentinvention, the intensity of the infrared ray is weakened on the overallsurface of the original document. Therefore, the abnormality can bejudged.

If an attempt is made to prevent the judgment by using an infrared rayreflecting film, the intensity of the near infrared ray is straightenedon the overall surface of the original document, the abnormality can bejudged.

If an intermediate-density infrared ray absorbing film or an infraredray reflecting film is used, the change of the reflectance of theidentification mark on the original document takes place usuallyalthough the base value deviates. Therefore, the judgment can beperformed.

As described above, the invisible information recording medium is usedas a recording medium for inhibiting copying and reading, the invisibleinformation recording medium having no information in the visible regionthereof and having the identification mark which is absorbed orreflected in the near infrared ray region. As a result, an effect can beobtained in that copying and reading of a medium having visibleinformation, copying or reading of which is intended to be inhibited,can be assuredly prevented by detecting the identification mark whilepreventing an influence upon the visible information.

Fifth Embodiment

According to this embodiment, toner particles containing a resin and acoloring agent are used as a developer for recording secret informationby an electrophotographic method. Further, the coloring agent is aninfrared ray absorbing coloring material or pigment which is free fromabsorption in the visible resion and absorption of which takes place inthe near infrared region. Therefore, secret recording can be performedwith a usual copying machine or in a usual photography.

Since use of the toner according to the present invention causes noimage to be present in the visible portion, another visible image can beformed with a usual toner which is free from absorption in the nearinfrared ray region. Therefore, the secrecy of information in the nearinfrared ray portion can further be improved.

The toner according to this embodiment is able to contain, as a coloringagent, an infrared ray absorbing coloring material or pigment which isfree from absorption in the visible portion but which is absorbed in thenear infrared ray portion.

The near infrared ray absorbing coloring material or pigment may be amaterial having the absorption wavelength peak in a range of 700 nm orlonger, preferably 750 nm or longer. Since the material having theabsorption wavelength peak in a range of 700 nm or shorter can bevisually detected, the secrecy cannot satisfactorily be maintained. If amaterial having the absorption wavelength peak in a range of 1100 nm orlonger is used, sensitivity of a Si-type photo-detection device, such asa CCD, deteriorates. In this case, the identification mark cannotaccurately be judged. It is further preferable to employ a coloringmaterial or pigment having the absorption wavelength peak in a range of1000 nm or shorter.

The foregoing near infrared ray absorbing coloring material or pigmentmay be dispersed or mixed with the binder while being combined with anultraviolet absorber or an antioxidant.

The near infrared ray absorbing coloring material or pigment must be atype that does not absorb visible rays. The absorbance of the maximumabsorbing wavelength in the infrared ray region must be 5 times or morethe absorbance of the maximum absorbing wavelength, more preferably 10times or more.

If it is 5 times or less, it can easily visibly be recognized in avisible ray region if the mark in the near infrared ray region isallowed to have a thickness that can be identified. Therefore, anadverse influence is resulted on the information to be recorded.

More specifically, any one of the following near infrared ray absorbingcoloring material or pigment may be used. However, a material may beused regardless of the exemplified materials if it absorbs near infraredrays and exhibits large absorbance and excellent weathering and lightresistance.

Compounds (1) to (44)

The binder resin for use in the foregoing near infrared ray absorbingcoloring material or pigment may be a urea resin, melamine resin, alkydresin, acryl resin, vinyl chloride resin, aromatic sulfonamide resin, ora benzoquanamine resin or their copolymer.

    __________________________________________________________________________    (1)                                                                               ##STR183##                                          .sub.max =  820                                                               nm                    (2)                                                                               ##STR184##                                          .sub.max =  798                                                               nm                    (3)                                                                               ##STR185##                                          .sub.max =  773                                                               nm                    (4)                                                                               ##STR186##                                          .sub.max =  790                                                               nm                    (5)                                                                               ##STR187##                                          .sub.max =  800                                                               nm                    (6)                                                                               ##STR188##                                          .sub.max =  796                                                               nm                    (7)                                                                               ##STR189##                                          .sub.max =  793                                                               nm                    (8)                                                                               ##STR190##                                          .sub.max =  801                                                               nm                    (9)                                                                               ##STR191##                                          .sub.max =  819                                                               nm                    (10)                                                                              ##STR192##                                          .sub.max =  769                                                               nm                    (11)                                                                              ##STR193##                                          .sub.max =  785                                                               nm                    (12)                                                                              ##STR194##                                          .sub.max =  778                                                               nm                    (13)                                                                              ##STR195##                                          .sub.max =  928                                                               nm                    (14)                                                                              ##STR196##                                          .sub.max =  816                                                               nm                    (15)                                                                              ##STR197##                                          .sub.max =  927                                                               nm                    (16)                                                                              ##STR198##                                          .sub.max =  1050                                                              nm                    (17)                                                                              ##STR199##                                          .sub.max =  1010                                                              nm                    (18)                                                                              ##STR200##                                          .sub.max =  787                                                               nm                    (19)                                                                              ##STR201##                                          .sub.max =  785                                                               nm                    (20)                                                                              ##STR202##                                          .sub.max =  794                                                               nm                    (21)                                                                              ##STR203##                                          .sub.max =  796                                                               nm                    (22)                                                                              ##STR204##                                          .sub.max =  771                                                               nm                    (23)                                                                              ##STR205##                                          .sub.max =  790                                                               nm                    (24)                                                                              ##STR206##                                          .sub.max =  831                                                               nm                    (25)                                                                              ##STR207##                                          .sub.max =  940                                                               nm                    (26)                                                                              ##STR208##                                          .sub.max =  805                                                               nm                    (27)                                                                              ##STR209##                                          .sub.max =  1060                                                              nm                    (28)                                                                              ##STR210##                                          .sub.max =  944                                                               nm                    (29)                                                                              ##STR211##                                          .sub.max =  954                                                               nm                    (30)                                                                              ##STR212##                                          .sub.max =  1090                                                              nm                    (31)                                                                              ##STR213##                                          .sub.max =  1090                                                              nm                    (32)                                                                              ##STR214##                                          .sub.max =  840                                                               nm                    (33)                                                                              ##STR215##                                          .sub.max =  772                                                               nm                    (34)                                                                              ##STR216##                                          .sub.max =  765                                                               nm                        ##STR217##                                                                (35)                                                                              ##STR218##                                          .sub.max =  790                                                               nm                        ##STR219##                                                                (36)                                                                              ##STR220##                                          .sub.max =  835                                                               nm                    (37)                                                                              ##STR221##                                          .sub.max =  858                                                               nm                    (38)                                                                              ##STR222##                                          .sub.max =  855                                                               nm                    (39)                                                                              ##STR223##                                          .sub.max =  1010                                                              nm                    (40)                                                                              ##STR224##                                          .sub.max =  770                                                               nm                    (41)                                                                              ##STR225##                                          .sub.max =  765                                                               nm                    (42)                                                                              ##STR226##                                          .sub.max =  870                                                               nm                    (43)                                                                              ##STR227##                                          .sub.max =  875                                                               nm                    (44)                                                                              ##STR228##                                          .sub.max =  905       __________________________________________________________________________                                                            nm                

The toner according to the present invention may comprise an adequateresin material. If the toner is used in a full color electrophotographicmethod, it is preferable to use a substantially transparent resinmaterial. Although the toner may contain the resin comprising thesubstantially transparent resin material, it is preferable to use aresin having other preferred characteristics.

It is preferable that a resin of a type which is in the form of, forexample, a non-viscous solid at room temperature as to be used easily inan ordinary electrophotographic process.

It is preferable that the resin be a thermoplastic resin having amelting point higher than room temperature and lower than a level atwhich usual paper tends to be burnt black so that the resin can bemelted on the paper when heated at the time of generating a toner imageon the paper or transferring the same on to a paper copying sheet.

It should be noted that the necessity of meeting the foregoingconditions can be eliminated. The reason for this is that a resin havinga higher melting point may be used and that the foregoing resin is usedin another method (for example, U.S. Pat. No. 2,776,907 invented byCarlson) of applying vapor of a solvent with respect to the foregoingresin to a paper copying sheet for carrying a toner image so that it canbe melted onto the paper copying sheet.

The toner may, of course, be melted onto another surface.

However, the foregoing surface enables the heating value required tomelt the toner onto the foregoing surface to be adjusted due to its heatconductivity and wet characteristics. Further, it is preferable that thetoner resin have-excellent frictional charging characteristics andsatisfactory insulating characteristics to charge electricity as to beused in development in various electrophotographic method, such as acascade development of an electrophotographic latent image disclosed inU.S. Pat. No. 2,618,552 invented by Wise and U.S. Pat. No. 2,638,416invented by Walkup and Wise and the other known development method inthe related technical field or an electrostatic powder image transfermethod disclosed in U.S. Pat. No. 2,576,047 invented by Shaffart andU.S. Pat. No. 2,626,865 invented by Mayo.

Although an arbitrary and adequate transparent resin may be used in thetoner according to the present invention, use of an esterified productcomposed of a vinyl resin and diol comprising dicarboxylic acid anddiphenyl will enable excellent result to be obtained.

The toner according to the present invention may comprise an arbitraryand adequate vinyl resin. The vinyl resin may be a homopolymer or acopolymer of two or more types of vinyl monomers. Typical monomers foruse to manufacture the vinyl polymer are exemplified by the followingmaterials.

Styrene; p-chlorostyrene; vinyl naphthalene; ethylene unsaturatedmonoolefin such as ethylene, propylene, butylene or isobutylene; vinylester such as vinyl chloride, vinyl bromide, vinyl fluoride, vinylacetate, vinyl propionate; vinyl benzonate; vinyl butyrate; α-methylenealiphatic monocarboxylic acid such as methyl acrylate, ethyl acrylate,n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate,2-chloroethyl acrylate, phenyl acrylate, α-chloroacrylate, methylmethacrylate, ethyl methacrylate or butyl methacrylate; acrylonitryl,methacrylonitryl or acryl amide; vinyl ether such as vinyl methyl ether,vinyl isobutyl ether or vinyl ethyl ether; vinyl ketone such as vinylmethyl ketone, vinyl hexylketone or methyl isobrophenyl ketone;halogated vinylidene such as vinylidene chloride or vinylidene chlorinefluoride; N-vinyl compound such as N-vinyl pyrol, N-vinyl carbazole,N-vinyl indol or N-vinyl pyloridone; and their mixture.

The vinyl resin suitable for use in the toner usually has weight averagemolecular weight of about 3,000 to 500,000.

It is preferable to use a toner of a type containing a styrene resin ina relatively large quantity.

A further thick image can be obtained if the styrene resin is present inthe toner in a quantity of 25 wt % or more of the overall weight of theresin in the toner. The styrene resin may be a homopolymer of styrene ora homolog of styrene or may be a copolymer of styrene and anothermonomer having a single methylene group bonded to a carbon atom with adouble bond.

That is, monomers of a type that can be copolymerized with styrene byadditional polymerization are as follows.

P-chlorostyrene; vinyl naphthalene; ethylene unsaturated monoolefin suchas ethylene, propylene, butylene or isobutylene; vinyl ester such asvinyl chloride, vinyl bromide, vinyl fluoride, vinyl acetate, vinylpropionate, vinyl benzonate; vinyl butyrate; α-methylene aliphaticmonocarboxylic acid such as methyl acrylate, ethyl acrylate, n-butylacrylate, acrylic acid, isobutyl acrylate, dedecyl acrylate, n-octylacrylate, 2-chloroethyl acrylate, phenyl acrylate, α-chloroacrylate,methyl methacrylate, ethyl methacrylate or butyl methacrylate;acrylonitryl, methacrylonitryl or acryl amide; vinyl ether such as vinylmethyl ether, vinyl isobutyl ether or vinyl ethyl ether; vinyl ketonesuch as vinyl methyl ketone, vinyl hexylketone or methyl isobrophenylketone; halogated vinylidene such as vinylidene chloride or vinylidenechlorine fluoride; N-vinyl compound such as N-vinyl pyrol, N-vinylcarbazole, N-vinyl indol or N-vinyl pyloridone; and their mixture.

The styrene resin may be manufactured by polymerizing a mixture of twoor more types of the foregoing unsaturated monomers and a styrenemonomer.

The expression "additional polymerization" includes known methods, suchas a free radical polymerizing method, an anion polymerizing method, andan action polymerizing method.

The vinyl resin containing the styrene type resin may be mixed with oneor more types of the other resins.

In the case where the vinyl resin is mixed with the other resin, it ispreferable that the resin to be added be another vinyl resin.

The reason for this is that the obtainable mixture is characterized inthat excellent frictional charging stability and uniform resistanceagainst physical deterioration.

The vinyl resin to be mixed with the styrene resin or another resin maybe manufactured by additional polymerization of an adequate vinylmonomer, such as a vinyl monomer.

Another thermal plastic resin may be mixed with the vinyl resinaccording to the present invention.

Typical non-vinyl thermal plastic resins are exemplified by thefollowing materials.

In a case where phenol formaldehyde resin denatured with rosin, epoxyresin denatured with oil, polyurethane resin, fiber resin, polyetherresin or the resin component of a toner of their mixture contains amixture of styrene co-polymerized with another unsaturated monomer orpolystyrene and another resin, it is preferable that the styrene iscontained in a quantity of 25 wt % or more of the total weight of theresin present in the toner.

The reason for this is that a thicker image can be obtained.

A polymerized ester compound of dicarboxylic acid and diol containingdiphenyl may be used as a preferred resin for the toner according to thepresent invention, the diphenyl reactant having the following generalformula: ##STR229## where R is an alkylene group which comprises orwhich does not comprise a substituent having 2 to 12 carbon atoms oralkylidene group having 1 to 12 carbon atoms; R' and R" are alkylenegroups each of which comprises or which does not comprise a substituenthaving 2 to 12 carbon atoms, an alkylene group having 8 to 12 carbonatoms and allylene group; X and X' respectively are alkyl groups eachhaving 1 to 4 hydrogen or carbon atoms; n₁ and n₂ respectively are 1 orlarger and the average sum of n₁ and n₂ is smaller than 21. If R is thealkylidene group having 2 to 4 carbon atoms and R' and R" are alkylenegroups each having 3 to 4 carbon atoms, it is preferable to usediphenol.

The reason for this is that resistance against blocking can be enlarged,the clearness of characters is improved, and the toner image can furthercompletely be transferred.

The optimum result can be obtained in a case of diol in which R is anisopropylidene group and R' and R" are propylene group or butylenegroup.

The reason for this is that the resin manufactured from the foregoingdiol has strong resistance against aggregation and it is able to quicklypenetrate into a receiving paper sheet under the melted condition. It ispreferable that dicarboxylic acid having 3 to 5 carbon atoms be used.

The reason for this is that the obtained toner resin has strongresistance against the formation of the film on an image generatingsurface that can be used again. Further, it has strong resistanceagainst generation of fine powder under condition where the apparatus isbeing operated.

The optimum result can be obtained from use of α-unsaturateddicarboxylic acid containing fumaric acid, maleic acid or maleic acidanhydride. The reason for this is that it has the strongest resistanceagainst physical deterioration of the toner and it can be quicklydissolved.

If an unsaturated bond is present in the reactant of the α-unsaturateddicarboxylic acid, tough resin molecules can be obtained without adverseinfluence upon dissolving and crushing characteristics.

Any diphenyl expressed by the foregoing formula may be used. Typicaldiphenyl having the foregoing general structure is exemplified by thefollowing materials.

2,2-bis (4-β-hydroxyethoxyphenyl)-propane, 2,2-bis(4-hydroxyisopropoxyphenyl) propane, 2,2-bis(4-β-hydroxyethoxyphenyl)-pentane, 2,2-bis(4-β-hydroxyethoxyphenyl)-butane, 2-2-bis(4-hydroxy-propoxyphenyl)-propane, 2,2-bis (4-hydroxy-propoxyphenyl)propane, 2,2-bis (4-hydroxy-propoxyphenyl) propane, 1,1-bis(4-hydroxy-ethoxy-phenyl)-butane, 1,1-bis (4-hydroxyisopropoxyphenyl)heptane, 2,2-bis (3-methyl-4-β-hydroxyethoxyphenyl) propane, 1,1-bis(4-β-hydroxyethoxyphenyl)-cyclohexane, 2,2'-bis(4-6-hydroxyethoxyphenyl)-norvalnan, 2-2-bis (4-β-hydroxystryloxyphenyl)propane, polyoxyethylene ether of isopropylidene diphenol (the twophenolhydroxyl groups are oxyethlated and the average oxyethylene groupper mole is 2.6), polyoxypropylene ether of 2-butylidenediphenyl (thetwo phenol hydroxy groups are oxyalkylated and the average oxypropylenegroups is 2.5). It is preferable that diphenol is used in which R is analkylidene group having 2 to 4 carbon atoms and R' and R" are alkylenegroups each having 3 to 4 carbon atoms.

The reason for this is that resistance against formation into a blockcan be strengthened, the clearness of characters can be improved and thetone image transference can be performed further completely. The optimumresult can be realized in a case where diol is used which is selectedfrom a group in which R is isopropylidine and R' and R" are propyleneand butylene. The reason for this is that the resin obtainable from theforegoing diol has further strong resistance against formation of blocksand it can considerably quickly be penetrated into a paper receivingsheet under the melted condition.

Any arbitrary dicarboxylic acid is able to react with the foregoing diolso that the toner resin according to the present invention ismanufactured. The foregoing acid may be substituted, not substituted,saturated or not saturated. The foregoing acid is expressed by thefollowing general formula:

    HOOCR'"n.sub.3 COOH

where R'" is an alkylene group which has a substituent or which has nosubstituent and which has 1 to 12 carbon atoms, an allylene group or analkylene allylene group having 10 to 12 carbon atoms, and n₃ is smallerthan 2. In this specification ("What is claimed is" included), theexpression "dicarboxylic acid" includes anhydride of the foregoing acid(a case where the hydride is present). Typical dicarboxylic acidincludes the following materials: oxalic acid, malonic acid, succinicacid, glutaric acid, adipic acid, pimeric acid, suberic acid, azelaicacid, sebacic acid, phthalic acid, mesaconic acid, homophthalic acid,isophthalic acid, telephthalic acid, O-phenyl acetate-β-propionic acid,itaconic acid, maleic acid, maleic anhydride, fumaric acid, phthalicanhydride, traumatinic acid, and citraconic acid.

It is preferable to use dicarboxylic acid having 3 to 5 carbon atoms.The reason for this is that the obtainable toner resin has strongresistance against formation of film on the image generating surfacethat can be used again. Further, it has resistance against generation offine powder in a state where the apparatus is being operated. Theoptimum result can be obtained from α-unsaturated dicarboxylic acidincluding fumaric acid, maleic acid or maleic anhydride.

The reason for this is that maximum resistance against physicaldeterioration of the toner can be obtained, and molten substance canquickly be obtained. Although the mechanism has not been cleared yet, itcan be considered that the presence of an unsaturated bond in thea-unsaturated dicarboxylic acid reactant enables further tough resinmolecules to be obtained while preventing an adverse influence upon themelting characteristics and crushing characteristics.

The polymerized esterified product to be contained in the toneraccording to the present invention may be copolymerized or mixed withone or more thermal plastic resins if necessary. If it is mixed withanother thermal plastic resin, it is preferable that the resin to beadded is an aromatic resin, an aliphatic resin or their mixture. Thereason for this is that the obtainable mixture has uniform density andexcellent prediction for each batch due to its physical properties. Agreat number of types of thermal plastic resins is able to mix with theresin according to the present invention. Typical thermal plastic resinsare as follows.

Formaldehyde resin denatured with rosin, epoxy resin denatured with oil,polyurethane resin, fiber resin, vinyl resin and their mixture.

If the resin component in the toner contains the additive resin, theadditive component must be contained in a quantity of about 50 wt % orless with respect to the overall weight of the resin present in thetoner. It is preferable that the condensation-polymerized product ofdiol and dicarboxylic acid be present in a relatively large quantity inthe resin component of the toner. The reason for this is that themelting temperature is further lowered if the additive material is addedin a predetermined quantity. If the condensation-polymerized product ofdiol and dicarboxylic acid is contained in the toner in a largequantity, a clearer and thicker image can be obtained. The additiveresin may be contained in the toner mixture by any one of methodsselected from a group consisting of a hot melting method, a solventmethod and an emulsifying method. The obtainable resin mixture and thecopolymer have a substantially uniform characteristic and they aresatisfactorily adaptable to the pigment and the dye. The coloring agentmay be added prior to, simultaneously with or after performing thepolymerizing process.

It is preferable that an adequate vinyl resin or a polyester alkyd resinbe added to the toner according to the present invention. The optimumresult can be obtained in electrophotography if any one of the followingmaterials is used which is selected from a group consisting ofstyrene-butyl methacrylate copolymer, styrene-vinyl toluene copolymer,styrene-acrylate copolymer, polystyrene resin, a resin mainly composedof styrene of a type disclosed in Reissue U.S. Pat. No. 25,136 disclosedby Carlson, a resin mainly composed of polystyrene, and a polystyrenemixture disclosed in U.S. Pat. No. 2,788,288 by Rheinfrank and Jones.

The toner composition according to the present invention can bemanufactured by any one of known toner mixing methods and crushingmethods. For example, a method may be employed in which the componentsare mixed and kneaded, and the obtained mixture is fined to sufficientlymix the components. The toner particles can be formed by another knownmethod, such as a method using a suspension fluid of the tonercomposition, a method using a hot molten substance or a method ofspraying and drying a solution.

If the toner mixture according to the present invention is adapted to acascade development method, the toner must have an average particle sizeof about 30 μ or less. In order to obtain the optimum result, it ispreferable that the average particle size ranges about 5 to about 17 μ.If the toner mixture is used in the powder cloud development method, itis preferable that the particle size be slightly smaller than 1 μ.

A coated or non-coated carrier substance has been known which isadaptable to the cascade development method or the magnetic brushdevelopment method.

The carrier particles may be electroconductive, insulating, magnetic ornon-magnetic particles. However, the necessity lies in that the carrierparticles are supplied with a charge, the polarity of which is oppositeto the polarity of the toner particles when the toner particles adhereto the carrier particles and the carrier particles are brought intocontact with the toner particles as to surround the toner particles. Ifpositive copying of an electrostatic latent image is required, thecarrier particles must have a charge, the polarity of which is oppositeto the magnetism of the electrostatic latent image. If inverse copyingof the electrostatic latent image is desired, the carrier particles musthave the same polarity as that of the electrostatic latent image.

As described above, the material of the carrier particles is selecteddepending upon the frictional charging characteristics in relation tothe toner to be charged such that a first component of the developer ischarged positively if the residual component of the developer is at alower position in the frictional charging sequence with respect to thefirst component of the developer. On the other hand, the residualcomponent is charged negatively if the residual component is at an upperposition than the position of the first component in the frictionalcharging sequence. By adequately selecting the material depending uponthe influence of the frictional charge of the material, the chargedpolarity of the materials is made as follows at the time of theforegoing mixture: the charged toner particles adhere to the surfaces ofthe carrier particles as to be coated on the surfaces while beingallowed to adhere to the portions of the electrostatic image carryingsurfaces having larger attracting force.

Typical carriers are exemplified by sodium chloride, ammonium chloride,aluminum potassium chloride, Rochelle salt, sodium nitrate, methylmethacrylate, glass and silicon dioxide. The carrier may be usedtogether with the coating material or used without the coating material.

A large portion of the typical carriers has been disclosed in U.S. Pat.No. 2,618,551 and U.S. Pat. No. 2,638,416 respectively disclosed by L.E. Warcup and U.S. Pat. No. 2,618,552 disclosed by E. N. Wise.

It is preferable to use carrier particles each having a diameter ofabout 50 to about 1,000 μ and finally coated.

The reason for this is that the carrier particles have sufficientdensity and inertia to prevent the adhesion to the electrostatic image.The adhesion of the carrier particles to the surface of thephotosensitive drum must be prevented because the surface is caused tohave a deep flaw in a case where cleaning is performed by a web cleanerusing a web arranged as disclosed in U.S. Pat. No. 3,186,838 disclosedby W. P. Graff, Jr. and the like during the process of transferring theimage and during the process of cleaning the drum.

When the carrier particles are allowed to adhere to the image generatingsurface of the photosensitive member, deletion of copying takes place.In general, a satisfactory result can be obtained when a toner in aquantity of about one part by weight is used together with about 10 toabout 200 parts of the carrier.

The toner composition according to the present invention can be used toform an electrostatic latent image on an ordinary photoconductivesurface and an adequate electrostatic latent image holding surface.

Typical photoconductive substances have been disclosed in U.S. Pat. No.2,803,542 filed by Walrich, U.S. Pat. No. 2,970,906 filed by Bixby, U.S.Pat. No. 3,121,007 filed by Middleton, and U.S. Pat. No. 3,151,982 filedby Corrsin.

50 parts by weight of a copolymer of 65 parts by weight of styrene and35 parts by weight of butyl methacrylate and 1 part by weight oftransparent infrared ray absorbing coloring material (SIR-159manufactured by Mitsui Toatsu) were used so that an infrared rayabsorbing toner mixture was prepared. The infrared ray absorbing tonermixture was melted and previously mixed, and then the composition waskneaded in a roll mill so that the near infrared ray absorbing coloringmaterial was uniformly dissolved and dispersed. The obtained compositionwas cooled, and fined by a jet crushing machine so that near infraredray absorbing toner having an average particle size of 10 μm wasobtained.

Sixth Embodiment

The toner according to the fifth embodiment and the two-componentcascade developer disclosed in U.S. Pat. No. 2,618,551 were mixed. Theforegoing toner was allowed to adhere to the electrostatic latent imageformed on an image carrier comprising an OPC by a cascade developmentmethod so that the image was developed. Then, the image was transferredto paper by an electrostatic transfer method before it is melted andfixed by a hot roller.

The obtained record could not visually be judged. Reflection spectrummeasured with a spectrum light intensity meter Shimazu UV-3100S is shownin FIG. 22.

FIG. 22 shows the reflection spectrum of the paper used in the foregoingprocess.

Seventh Embodiment

The image recorded in the process according to the sixth embodiment wasread by a digital copying machine (CLC-500 manufactured by Canon) havingthe filter shown in FIG. 23, and the read image was converted into avisible image which was then transmitted, resulting in an excellentimage to be obtained.

Eighth Embodiment

The image recorded on the paper in the process according to the sixthembodiment was intended to be read and copied by the digital copyingmachine (CLC-500 manufactured by Canon) having a usual filter, resultingin no image to be obtained.

As described above, the toner particles containing the resin and thecoloring agent were used as the developer for recording secretinformation by the electrophotographic method. The fact that thecoloring agent is the near infrared ray absorbing coloring material orpigment which does not absorb visible rays but which absorbs nearinfrared rays enables an effect to be obtained in that secret recordingcan be performed with a usual copying machine or in a usual photography.

According to the present invention, there are provided a recordingmedium having invisible information for assuredly judging a specificimage such as a bill with a low cost and an invisible informationdetection apparatus capable of detecting and utilizing the foregoingmark.

According to the present invention, there is provided an invisibleinformation recording medium serving as recording paper capable ofeasily identifying a specific original document which must not becopied.

According to the present invention, there is provided a novel recordingmaterial for use in an image forming apparatus, such as a copyingmachine, and more particularly, in an electrophotographic apparatus.

Although the invention has been described in its preferred form with acertain degree of particularly, it is understood that the presentdisclosure of the preferred form can be changed in the details ofconstruction and the combination and arrangement of parts may beresorted to without departing from the spirit and the scope of theinvention as hereinafter claimed.

What is claimed is:
 1. An invisible information detection apparatuscomprising:irradiation means for irradiating a light onto a medium;detection means for detecting invisible information which is defined byan infrared light generated from the medium, in accordance with theirradiation by said irradiation means; and judgement means for judging aspecific pattern consisting of a plurality of same shape patterns on themedium from reflection characteristics of the medium corresponding tosaid detected invisible information, wherein one of said same shapepatterns represents higher reflectance than reflectance of the medium insubstantially same infrared wavelength region and the other of said sameshape patterns represents lower reflectance than the reflectance of themedium.
 2. An apparatus according to claim 1, wherein said irradiationmeans irradiates the light onto the medium, and a wavelength of thelight irradiated has a difference of at least 50 nm from a wavelength ofthe infrared wavelength region.
 3. An apparatus according to claim 2,wherein the infrared wavelength region is a wavelength region of 700 mto 1100 nm.
 4. An apparatus according to claim 1,wherein said detectionmeans detects invisible information which is defined by an excitationlight excited by the light irradiated by said irradiation means.
 5. Anapparatus according to claim 4, wherein the irradiated light is anultraviolet light.
 6. An apparatus according to claim 4, wherein theirradiated light is a visible light.
 7. An apparatus according to claim1, wherein the medium has substantially constant reflectance for theirradiated light of 450 nm to 1200 nm.
 8. An apparatus according toclaim 1, further comprising:reader means for reading visible informationof the medium; and process means for processing the read visibleinformation in accordance with a judgment result of said judgment means.9. An apparatus according to claim 8, wherein, in a case where thejudgment result directs that the specific image is not judged, saidprocess means performs an image formation according to the visibleinformation.
 10. An apparatus according to claim 8, wherein, in a casewhere the judgment result directs that the specific image is judged,said process means does not perform an image formation according to thevisible information.
 11. An apparatus according to claim 1, furthercomprising reader means for reading visible information of the medium,andwherein said judgment means performs the judgment in accordance withthe detection result and the read visible information.
 12. An invisibleinformation detection method comprising:an irradiation step ofirradiating a light onto a medium; a detection step of detectinginvisible information which is defined by an infrared light generatedfrom the medium, in accordance with the irradiation in said irradiationstep; and a judgement step of judging a specific pattern consisting of aplurality of same shape patterns on the medium from reflectioncharacteristics of the medium corresponding to said detected invisibleinformation, wherein one of said same shape patterns represents higherreflectance than reflectance of the medium in substantially sameinfrared wavelength region and the other of said same shape patternsrepresents lower reflectance than the reflectance of the medium.